The purpose of this one-year planning grant is to design research objectives and methodological procedures necessary to study the effectiveness and efficacy of a comprehensive and integrated classroom curriculum for preschool children. The STAR curriculum promotes school readiness and early school success and is tailored to meet the needs of children who are at increased risk for learning and adjustment difficulties due to factors associated with poverty. The large-scale, multidisciplinary investigation will be designed to accomplish four aims. The first aim is to study the effectiveness of the STAR curriculum for specific subgroups of at-risk children. Integral to effectiveness is quality implementation; thus the second aim is to test the effectiveness of the support and training structures required to develop and maintain high-quality curriculum implementation and sustainability. The third aim is to measure variation in the impact of the STAR curriculum attributable to variation in experimentally manipulated curriculum components, as well as naturally occurring sources of variation in the child, in the social contexts of family, in classrooms and programs, and in peers. In preparation for the large-scale study, we propose to use this planning grant to achieve the following objectives: 1) Establish a collaborative multidisciplinary team to finalize research objectives and approaches; 2) Finalize site selection and develop subject recruitment procedures; 3) Specify measurement approaches for constructs related to child, family, teacher, classroom, and system variables; 4) Align research design and data analysis strategies to investigate both the professional development structures necessary for high-quality implementation and sustainability, as well as the impact of curriculum components; and 5) Prepare training materials associated with implementation of the STAR curriculum and professional development frameworks.